How to Identify the Indian State / Union Territory / Metro a BSNL cellphone belong to?

I came across this table below to identify the home state (Indian) to which a a BSNL (Bharat Sanchar Nigam Ltd) cellphone belong to. For example, if the cell phone number is 9447100100, its first 4 digits are 9447, which belong to Kerala state as per the lookup table given below.